Re: [Xen-devel] vmx: VT-d posted-interrupt core logic handling

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, March 10, 2016 5:06 PM
> 
> 
> > There are many linked list usages today in Xen hypervisor, which
> > have different theoretical maximum possible number. The closest
> > one to PI might be the usage in tmem (pool->share_list) which is
> > page based so could grow 'overly large'. Other examples are
> > magnitude lower, e.g. s->ioreq_vcpu_list in ioreq server (which
> > could be 8K in above example), and d->arch.hvm_domain.msixtbl_list
> > in MSI-x virtualization (which could be 2^11 per spec). Do we
> > also want to create some artificial scenarios to examine them
> > since based on actual operation K-level entries may also become
> > a problem?
> >
> > Just want to figure out how best we can solve all related linked-list
> > usages in current hypervisor.
> 
> As you say, those are (perhaps with the exception of tmem, which
> isn't supported anyway due to XSA-15, and which therefore also
> isn't on by default) in the order of a few thousand list elements.
> And as mentioned above, different bounds apply for lists traversed
> in interrupt context vs such traversed only in "normal" context.
> 

That's a good point. Interrupt context should have more restrictions.

Thanks
Kevin

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